1. Field of the Invention
The present invention relates to a method of fabricating an analog capacitor integrated circuit device, and more particularly, to a method of forming an analog capacitor integrated circuit device in which the double polysilicon capacitor and dual gate processes are combined.
2. Description of the Prior Art
Capacitors are critical components in the integrated circuit devices of today. For example, in analog integrated circuit devices, capacitors play an important role. High value resistors are not necessary in analog capacitor applications. Conventionally, the double poly capacitor process to make an analog capacitor and the dual gate process are separate modules. First, a thin gate oxide is formed, then the thick gate oxide is formed. The thick gate oxide formation typically involves two oxidation steps and photoresist stripping steps. The thick gate oxide resulting from this process may have poor integrity. After transistor formation, the capacitor process module is inserted, having capacitor dielectric and polysilicon depositions to form the capacitor plate and resistor. The additional thermal budget used for the capacitor and resistor will impact the transistors. It is desired to simplify the existing process and to modify the design for the polysilicon layer and capacitor mask so that the dual gate and double poly capacitor modules can be integrated in the analog capacitor process.
U.S. Pat. Nos. 5,843,817 to Lee et al and 5,858,831 to Sung teach logic and embedded memory integration methods. U.S. Pat. No. 5,668,035 to Fang et al teaches a dual gate process. U.S. Pat. No. 5,670,410 to Pan teaches fabrication of an analog capacitor using an oxide capacitor dielectric layer. None of these patents show the integration of dual gate and double poly capacitor processes for an analog capacitor integrated circuit device.